This invention relates generally to the construction and assembly of two-piece pressure vessels or bodies for containing pressurized fluid, and more particularly to methods and apparatus for the improved retention of the top part of such bodies (e.g., xe2x80x9cbonnetsxe2x80x9d) upon the bottom (e.g., base) thereof. In a more particular sense, the invention relates to methods and apparatus for the securement of pressure regulator bonnets upon their underlying regulator body, and to improvements therein which enable the use of thinner, stamped sheet metal bonnets under pressure conditions which would have previously threatened failure due to bonnet distortion and resultant loosening.
In the past, pressure regulators and other such devices having an interconnected top and bottom defining hollow interior utilized cast metal parts for the top and bottom parts, and the top was secured to the bottom by a circumferential series of screws or the like which extended through holes in one such part (e.g., the top) and engaged corresponding threaded apertures in the other such part (e.g., the bottom). This produced sturdy and reliable pressure containers, but the fabrication and assembly was labor-intensive, time-consuming, and expensive. Due to the ever-present need for decreased manufacturing expense and lower product cost, various alternative methods of securement have been proposed and to some extent utilized over time. One such alternative which proved to be very effective was a process by which an upraised annular ridge or the like was integrally cast onto the bottom part and this was then forcibly deformed radially inwardly during assembly so as to overlie the perimetral edge of the upper body part, i.e., the bonnet. The approach could be automated, and proved quite effective when properly executed, but since the metal to be deformed extended all of the way around the lower body, the process was not necessarily simple to implement and required various special measures to carry it out properly. One such approach involved the use of an undulating deformation of this retaining ridge, to accommodate the excess material which occurred as the top of the annular ridge was forced radially inward and thus acquired a smaller circumference. This process produced a crimped xe2x80x9cbottle capxe2x80x9d appearance, and it was quite effective and advantageous but did have certain minor disadvantages as well.
With increasing price competition and the ever-present need for less expensive manufacturing techniques, the concept of using a less expensive bonnet made of stamped metal rather than cast metal has emerged, but the secure and reliable retention of such a bonnet on the regulator body or other such element raises new difficulties, largely due to the fact that the thinner, stamped bonnet is more subject to being deformed by excess pressures which can occur inside the assembled pressure body. Bonnet distortion due to overpressure may result in various irregular shape changes, but most or all of these include some bulging or ballooning of the bonnet outwardly over its central portions, with resultant radially inward movement of the perimeter, and this often or even usually will destroy the integrity of the bonnet edge retention and perhaps even release the bonnet so that it is blown off the top of the regulator.
The present invention is based on an apprehension of the problems noted above that apply with respect to use of thin, lightweight, stamped, or other such bonnets for pressure regulators and other such pressurized devices, and provides a unique and effective solution for the same that yields significant manufacturing economies.
Generally stated, the invention provides a novel cooperative and interacting bonnet and base component structure, by which the bonnet is made to be initially self-retaining against regulator diaphragm spring pressure or the like acting to displace the bonnet from the body prior to final assembly, and which is also easily and readily subjected to final assembly by cold-flow metal-forming techniques analogous to riveting or swedging, pursuant to which portions of the base component are deformed radially inwardly over edge portions of the bonnet and in addition certain interlocking structural pairs of the bonnet and base become engaged with one another. This engagement acts to lock the periphery of the bonnet in place upon the base and prevent disengagement thereof due to radially inward stresses applied to the bonnet edges as a result of deforming overpressure conditions.
Accordingly, the invention provides both a novel structure and a novel method of assembly, for achieving the foregoing purposes.